Southern California -- this just in

A new study by California health officials says pregnant women with flu-like symptoms should promptly undergo “aggressive antiviral treatment,” even if a preliminary test shows that the patient tests negative for the flu.

The study, published online today by the New England Journal of Medicine, is the latest urging physicians to consider prescribing antiviral drugs like Tamiflu to patients earlier, even in the absence of lab tests that confirm a flu diagnosis.

A preliminary flu test, which can be completed in minutes, has a high rate of error and can mistakenly lead doctors to believe a patient does not have the flu. Out of 153 women of child-bearing age who were tested and hospitalized with H1N1 virus between April and August in California, nearly 40% received an incorrect preliminary test result. Erroneous test results may cause doctors to delay prescribing antiviral drugs.

“They should not rely on rapid tests. We found the rapid tests were not very sensitive, and some doctors, when looking at the charts, actually delay treatment,” said Dr. Janice Louie, chief of the influenza and respiratory diseases section for the California Department of Public Health.

Louie recommended that clinicians consider prescribing antiviral drugs to ill pregnant women suspected of having the flu while they wait for the results of a more accurate test, which can take days.

Delaying antiviral treatment to H1N1-infected pregnant women can have serious consequences.The state’s scientists have found that pregnant women who received antiviral drugs late — more than two days after the onset of illness — were four times as likely to require admission to the intensive care unit or die.

In some cases, researchers said the pregnant women did not immediately seek medical attention after falling ill; in other cases, doctors delayed prescribing antiviral drugs.

Out of data compiled from 102 pregnant and postpartum women hospitalized for H1N1 in California, eight died. None of those women received early antiviral treatment. In six of those cases, the preliminary rapid test gave an erroneous result.

One reason for the relative inaccuracy of the preliminary flu test is that it was developed for the seasonal flu virus, not H1N1, also known as the swine flu. “This is a new flu virus with different surface proteins. It’s not surprising that it might not be as sensitive in detecting a new flu virus,” Louie said.

California’s recommendation for quicker administration of antiviral drugs has been echoed by other health officials.

In another report published by the New England Journal of Medicine earlier this month, Dr. Tim Uyeki, a scientist with the CDC’s influenza division, wrote that “antiviral treatment should be started as soon as possible for hospitalized patients with suspected 2009 H1N1 and not withheld, because a negative [rapid test result] does not exclude 2009 H1N1 virus infection. Nor should treatment be delayed” until results from the more accurate tests are available, he wrote.

According to California health officials, pregnant women comprised 10% of those patients who were hospitalized with, or died from, H1N1 flu in California between April and August. An earlier report said that pregnant women were hospitalized at about quadruple the rate of the general population.